HOUSTON — A flurry of reports from Russia about the discovery of fragments of an alien spaceship at the site of the 1908 Tunguska explosion may be nothing more than wish fulfillment by devotees of a half-century-old Russian space myth, or they may actually have been based on genuine spacecraft fragments — but of Russian origin.

Either way, or even in the highly unlikely event the reports turn out to be credible, these stories reflect the way the century-old Tunguska blast continues to resonate in the human psyche.

Expedition leader Yuri Lavbin prefers the alien technology interpretation. That’s the theory he admits he started with, even before he got to the area. But other space experts have pointed out that the region is a drop zone for discarded rocket stages launched into space from Russia’s Baikonur base, and in fact was the crash site of one prototype manned space capsule at the very dawn of the space age.

On June 30, 1908, residents of southern Siberia spotted a dazzling fireball crossing the sky, followed by a flare brighter than the sun. Minutes later, a shock wave knocked many of those residents off their feet. When later expeditions reached the nearly inaccessible swamps where the explosion had occurred, they found trees flattened down in a pattern pointing away from ground zero — but no crater, and no meteorite fragments.

The first Soviet expedition was sent to the site in 1927, in hopes of finding metallic ore. Although a series of natural theories followed over the years, a Russian scientist and science-fiction author who visited Hiroshima in late 1945 postulated that the Tunguska blast, too, must have been nuclear in nature — and hence, the result of a visit by space aliens.

But Dutch space historian Geert Sassen suggests an earthly origin for the space fragments reportedly just found, and they could well have no connection with the 1908 event. “They might have found some parts of the fifth Vostok test flight,” he told associates via e-mail.

Sassen was referring to a flight on Dec. 22, 1960, meant to carry two dogs into space. According to “Challenge to Apollo,” NASA’s definitive history of the space race, "the payload landed about 3,500 kilometers downrange from the launch site in one of the most remote and inaccessible areas of Siberia, in the region of the Podkamennaya Tunguska River close to the impact point of the famed Tunguska meteorite."

A team of space engineers located the capsule, disarmed the destruct system, and rescued the canine passengers.

Natural explanations
Initially, astronomers were attracted to the idea that the object had been a comet nucleus, to account for the explosion when it slammed into the atmosphere. They toyed with other theories, including proposals involving antimatter and “mini-black holes,” but for many years there were no reliable theories on what happens when large objects hit Earth’s atmosphere.

That changed in the 1980s, as observations of artificial and natural fireballs expanded, along with the power of computer simulations.

“When the first modern models for atmospheric impacts were published in 1993,” NASA asteroid expert David Morrison said, “it became clear that this was a stony body.” He suggested that it was “somewhere between an ordinary chondrite and a carbonaceous chondrite in physical properties.”

It couldn’t have been a “dirty snowball” — that is, a light, fluffy comet, he continued. “In contrast, cometary objects with this mass, of low density and/or icy composition, would explode tens of kilometers above the surface and cause no harm.” We know this now because Pentagon satellites have actually been observing such explosions for several decades.

Unfortunately, Morrison adds, “the old comet theory persists out of inertia.” As to current scientific thinking, he says “Tunguska was very likely a stony object about 60 meters [196 feet] in diameter that disintegrated explosively at an altitude of approximately 8 kilometers [5 miles].”

UFO versionsIt didn’t do the new Russian UFO story’s credibility much good that it first appeared on the pages of the newspaper Pravda on Tuesday. In Soviet days, Pravda was the propaganda arm of the Soviet Communist Party, but under new management, it became a tabloid-style scandal sheet with a special penchant for wild paranormal tales.

“Explorers believe they have discovered blocks of an extraterrestrial technical device,” the article stated, adding that they assumed it was the one that had crashed in 1908. After dismissing a century’s worth of scientific investigation into natural theories for the H-bomb-sized explosion, the article concluded: “The only real explanation can be linked with powerful electromagnetic phenomena,” presumably of artificial origin.

The head of the expedition, Yuri Lavbin, told journalists that his team had concluded that the object moved from west to east, not from southeast, on its approach to the explosion zone. Using satellite photographs, he identified search areas near the town of Poligus, and that is where he located the metal fragment.

Lavbin reported that he knew all along that the crash had been caused by a UFO, and that his expedition had been organized to find the proof. In his scenario, there was a natural object that threatened to destroy Earth, but aliens intervened to save our planet.

“I am fully confident and I can make an official statement that we were saved by some forces of a superior civilization,” he explained. “They exploded this enormous meteorite that headed toward us with enormous speed.”

Photographs of the fragments may become available in the near future, as well as the results of laboratory testing. This would help differentiate something truly alien from the space debris that the Russians have been scattering across the Tunguska region for the last 50 years.

History of a mystery
Sassen’s suggestion that the mysterious “space fragment” found in the Tunguska area is more likely to be of Russian origin than Martian origin is supported by decades of history during which the Soviet government tolerated public interest in UFOs as a way of camouflaging actual space and missile events. Many of the most famous Soviet UFO stories that are still promoted in Western books and on Internet sites have been traced back to original — but highly classified — military space missions.

The most spectacular Soviet “UFO wave” in history occurred over the southern part of the country in 1967 and 1968, when crescent-shaped giant spaceships were reported flying across the skies. Endorsed as “unexplainable” by top Russian scientists, the widely witnessed apparitions turned out to be secret tests of Soviet thermonuclear warheads diving back from orbit.

In 1978, the smoking gun of Soviet ufology was a “jellyfish” UFO that drifted through the skies of northwest Russia, zapping computers and panicking predawn witnesses. It turned out to be the contrails from a rocket carrying a spy satellite from a secret space base. A similar secret launch in September 1984, seen by the crews and passengers of several commercial airliners, sparked stories of death rays and alien attacks.

At the time, Moscow officials denied that such space and missile events were occurring — and some were borderline violations of arms control treaties. Thus, it was convenient to have an explanation for ordinary people who saw them in the skies and wondered what they could have been. So for a generation of Russians, “alien visitors” became the explanation of choice for unusual lights in the sky.

NBC News space analyst James Oberg spent 22 years at NASA's Johnson Space Center as a Mission Control operator and an orbital designer. He is the author of several books on UFOs as well as the Soviet space effort, including "UFOs and Outer Space Mysteries" and "Uncovering Soviet Disasters."